21. How much power will an AM transmitter, rated at 50 kW, radiate if it is modulated to 100%?
- 50 kW
- 25 kW
- 100 kW
- 75 kW
22. An AM modulator has output
S(t) = 20 cos(300πt) + 6 cos(320πt) + 6 cos (280πt)
Then what is the modulation index of the wave?
- More than 100%
- 0.93
- 0.6
- 0.3
23. Which one of the following is considered as an A.M. signal?
- Binary phase-shift keying (BPSK)
- Differential phase-shift keying (DPSK)
- Differential encoded PSK
- Quadrature PSK
24. The antenna current of an A.M. transmitter is 8 A when only carrier is sent, but it increases to 8.93 A when the carrier is modulated. Then what is the percentage modulation of the wave?
- 43.00%
- 70.14%
- 100.00%
- 57.00%
25. For an AM signal, the bandwidth is 10 kHz and the highest frequency component present is 705 kHz. What is the carrier frequency used for this AM signal?
- 695 kHz
- 700 kHz
- 705 kHz
- 710 kHz
26. In an AM system, for satisfactory operation, carrier frequency must be n times the bandwidth of message-signal. What is the value of n?
- > 2
- > 5
- > 10
- > 50
27. Consider the following statements about analog communication and multiplexing:
- Noise problem for analog communication has the greatest effect on TDM system.
- Noise problem for analog communication has the least effect on SDM system.
Which of these statements is/are correct?
- i only
- ii only
- Both i and ii
- Neither i nor ii
28. A carrier is amplitude modulated by 4 signals of frequency 10 kHz, 15 kHz, 20 kHz and 25 kHz. What is the bandwidth of the modulated signal?
- 25 kHz
- 50 kHz
- 140 kHz
- 70 kHz
29. What is the power contained in SSB transmission when the carrier power is 1 kW and the modulation index is 0.3?
- 22.5 W
- 90 W
- 300 W
- 1 kW
30. If two signals modulate the same carrier with different modulation depths of 0.3 and 0.9, the resulting modulation signal will
- be over-modulated
- have the resultant modulation limited to 1.0
- have the resultant modulation index around 0.82
- have the resultant modulation index around 0.95